Oenothera hartwegii subsp. maccartii
Syst. Bot. Monogr. 83: 212. 2007.
Herbs usually sparsely strigillose, sometimes glandular puberulent. Leaves 0.6–3.5 × 0.1–0.6 cm, fascicles of small leaves to 1.5 cm usually present in axils; blade usually narrowly lanceolate to lanceolate or oblanceolate, rarely linear, base attenuate, margins subentire or serrulate, usually crinkled-undulate or undulate. Flowers: buds with free tips 1–6 mm; floral tube 17–45 mm; sepals 11–27 mm; petals 10–30 mm; filaments 6–12 mm, anthers 5–9 mm; style 25–60 mm. 2n = 14, 28.
Phenology: Flowering Mar–Sep.
Habitat: Grasslands, sandy to gravelly soil, limestone, with Acacia, Larrea, Opuntia, Prosopis, and Yucca.
Elevation: 30–1500 m.
Tex., Mexico (Coahuila, Nuevo León, Tamaulipas).
Subspecies maccartii occurs on the south Texas Plains and along the Rio Grande from Kinney, Milam, Uvalde, and Val Verde counties south to southeastern Coahuila, central Nuevo León, and northwestern Tamaulipas.